Death Valley geology field trip

Harmony Borax Works

View of the rounded Furnace Creek Formation rocks seen from the Furnace Creek Visitor Center. Photo by M. Moreno, USGS.

Tracing the source of Death Valley's borax

The primary source of borate minerals gathered from Death Valley's playas is the 6-4 million year old Furnace Creek Formation. The Furnace Creek Formation forms the remarkably rounded, yellow, brown, and green foothills that are beautifully exposed around Zabriskie Point. The Formation is made up of over 5000 feet of mudstone, siltstone, and conglomerate. Most of the silty mudstones were originally deposited in lakebeds that predate the modern Death Valley basin. The borates were concentrated in these lakebeds from hot spring waters and altered rhyolite from nearby volcanic fields.